Avery, 23, has spent the 2013 season split between AA Bowie and AAA Norfolk in the Orioles farm system. The left-handed hitting outfielder is 29-for-37 in steal attempts this season, and is batting a combined .259 (118x455) with 70 runs scored. Avery appeared in 32 games for the Orioles last season, batting .223 (21x94) with 6 stolen bases.

Avery was originally selected by Baltimore in the 2nd round (50th overall) in the 2008 June Draft out of Cedar Grove High School in Ellenwood, GA (suburb of Atlanta).

Morse, 31, appeared in 76 games for the Mariners batting .226 (64x283) with 13 doubles, 13 home runs and 27 RBI. He was sidelined early in the season with a small fracture in the little finger of his right hand and missed 31 games while on the disabled list with a strained right quad from June 22-July 30.

Avery will report to AAA Tacoma for the remainder of the season. With this transaction the Mariners 40-man roster remains at 37 players (Avery was on Baltimore's 40-man roster).